Process for beneficiating ores



United States Patent PROCESS FOR BENEFICIATING ORES Robert E. Snow, Lakeland, Fla., assignor to International Minerals & Chemical Corporation, a corporation of New York No Drawing. Filed Sept. 18, '1958, Ser. No. 761,682

24 Claims. (Cl. 209-3) The present invention generally relates to a process for the beneficiation of ores. More particularly, this invention relates to the beneficiation of feldspathic rock materials and minerals. Still more particularly, it relates to a process for the preparation of potash spar concentrates and soda spar concentrates from mixtures of potash spar and soda spar. Specifically, the present invention relates to the recovery of potash spar concentrates and soda spar concentrates from flotation concentrates obtained in froth flotation processes for the recovery of feldspar, which flotation concentrates contain potash spar and soda spar.

Feldspar is the name of a group of minerals, specifically aluminosilicates of potassium, sodium, calcium, and rarely barium. The aluminosilicate of potassium or potash spar and the aluminosilicate of sodium or soda spar are commercially important. They are used as a ceramic fluxing agent, a source of alkalies and alumina, and as an ingredient in glass manufacture.

Theoretically pure feldspars of any type are not found in commercial quantities. The best potash spars usually contain a small percentage of soda spar and, similarly, the best soda spars usually contain a small percentage of potash spar. For some uses of feldspar, a particularly high ratio of potash spar to soda spar is desirable and for other uses of feldspar a particularly high ratio of soda spar to potash spar is desirable. For example, for electrical and dental porcelain uses, a high potash spar is needed.

Feldspar has for many years been beneficiated by milling methods utilizing magnetic separations. Froth flotation of feldspar is now employed commercially by many companies. Electrostatic beneficiation of feldspar is also of economic importance. One method of electrostatical- 1y beneficiating feldspathic ore is described in Lawver, United States Patent No. 2,805,771. Using the electrostatic method described in said patent, it is possible to separate chemically different feldspars, i.e., soda spar from potash spar, spars rich in alkali metal component, and the like.

In a froth flotation process for beneficiating feldspathic ore, a comminuted feldspathic ore is 'reagentized with soaps or cationic reagents. Flotation concentrates obtained in froth flotation processes may be upgraded electrostatically by the method described in the Lawver patent. Further, using the method described in the Lawver patent, potash spar may be substantially separated from soda spar in flotation concentrates so as to separately prepare a high potash spar concentrate and a high soda spar concentrate. The present invention is directed to the problem of improving the beneficiation of feldspar flotation concentrates.

It is an object of the present invention to provide a process for the beneficiation of feldspathic ores.

It is another object of the present invention to provide a process for the beneficiation of feldspar flotation concentrates.

It is a further object of the present invention to provide a process for the beneficiation of feldspar flotation concentrates containing soda spar and potash spar.

It is an additional object of the present invention to provide a process for preparing a high potash spar concentrate.

It is still a further object of the present invention to provide a process for preparing a high soda spar conceutrate.

It is a specific object of the present invention to treat a feldspar flotation concentrate so as to substantially increase the separation of potash spar from soda spar when the flotation concentrate is subjected to an electrostatic separation operation.

These and other objects of the invention will be apparent to those skilled in the art from the description of the invention.

In accordance with the present invention, it has been discovered that eminently satisfactory beneficiation of feldspar flotation concentrates can be achieved electrostatically by means of a series of critical and interdependent process steps.

Generally described, the present invention comprises treating a feldspar flotation concentrate with a siliceous material, heating the treated concentrate, inducing the heated concentrate to accept an electrical charge, and subjecting the charged concentrate to an electrostatic separation.

When beneficiating a feldspathic ore according to flotation procedures, the ore as received from the mine is, inter alia, comminuted to economical liberation so as to substantially liberate the feldspar particles from the gangue. The comminuted ore is subsequently subjected to a froth flotation operation with cationic reagents such as long chain aliphatic amine acid addition salts. The froth float product is high in feldspar content.

As hereinbefore set forth, this froth float feldspar concentrate may be beneficiated according to the method set forth in Lawver Patent No. 2,805,771. However, when the feldspar concentrate is first treated with a siliceous material in accordance with the present invention, a markedly improved beneficiation is obtained. Further, very satisfactory separation of potash spar from soda spar may be obtained using the subsequent electrostatic separation step.

The feldspar ore charged to the froth flotation process is usually comminuted to an extent such that further comminution prior to the electrostatic separation may not be necessary. The efliciency of the electrostatic separation of the treated flotation concentrate is to a degree dependent upon the particle size of the comminuted ore. Generally, the particles should be smaller than 4 mesh. The most satisfactory particle size range for feldspar beneficiation, from an economic standpoint, is where approximately of the particles are of a size between about 8 mesh and about 200 mesh, most of the particles preferably being between about 20 mesh and about 100 mesh size. Where the flotation concentrate is of a size that it falls substantially within the range of from about 8 mesh to about 200 mesh, further comminution and/or sizing may not be necessary; however, further comminution may be performed if necessary or de sirable.

The comminuted ore is mixed with Water, forming a pulp or slurry to which is added the necessary flotation reagents. The pulp is conditioned to insure mixing with the reagents and the flotation is effected in any of the well known types of flotation machines. The collecting reagents used to effect flotation of the feldspar minerals are generally of the cationic type and preferably of the amine type. Preferred amine-type reagents are long chain aliphatic amines, their addition salts, and derivatives thereof. The reagent is usually modified Xihe addition of fiuosilicic acid and/or hydrofluoric acid and/or an alkali metal fluoride. An oiling agent and a frothing agent are also usually added to the ore pulp. The cationic reagent has a selective aflinity for the feldsparminerals and floats the feldspar minerals during theflotationoperation.

As hereinbefore set forth,these cationic flotation concentrates may be upgraded in accordance with the electrostatic process set forth in the cited Lawver patent; however, it has now been determined that the electrostatic beneficiation is improved when the cationic flotation concentrate is treated witha siliceous material prior to the electrostatic separation.

In'accordance with this invention, the feldspar flotation concentrate, while still containing the cationic flotation reagent, is treated with a siliceous material. The siliceous material preferably makes maximum contact with the surface of the feldspar concentrate and accordingly the method of treatment is preferably one which insures good contact. A preferred method of treatment is to slurrythe cationic feldspar concentrate with the siliceous material; Another method is to vigorously mix 7 the feldspar concentrate and the siliceous material together while both are in the dry state. The siliceous material may also be sprayed on or powdered onto the feldspar concentrate. Mixing or scrubbing the feldspar concentrate and siliceous material together in an aqueous slurry is, however, preferred since good contact is readily obtained and this method has produced good results. The mixing or scrubbing is preferably for a period 'of.at least one minute and is usually for less than one hour. A longer period may, however, be used if desired.

Any siliceous material may be used in the process and includes silicon and its compounds. Preferred siliceous material comprises colloidal silica, silica gel, precipitsted silica, diatomaceous earth, alkali metal silicates, such as sodium silicate solutions, anhydrous sodium silicates, etc., the sodium silicates used-preferably having a SiO to Na O mole ratio within the range of from about 1:1 to about 3.75:1. The water soluble alkali metal metasilicates and orthosilicates maybe used and these are commercially available and commonly are known as water glass. Orthosilicate esters may also be used such as the lower molecular weight silicate esters, e.g., methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, etc. The siliceous material is used in amount-of from about 0.05 to about 50 lbs. per ton of solids treated and preferably from about 0.50 to about 40 lbs. perton of solids treated.

The treatment of the feldspar concentrate, while still containing the cationic reagent, with the siliceous material is preferably in an aqueous slurry. -It is also pre ferred that the pH of the slurry be adjusted to between about 2.0 and 12.0. At pH values above or below this range, the treatment is less eflective. A still further preferred pH range is from about 5.0 to about 7.0; that is, the treatment with the siliceous material is preferably slightly acidic.

.After the treatment of the feldspar flotation concentrate with the siliceous material, the treated flotation feldspar concentrate is prefe rably thoroughly washed and dewatered The thoroughly washed and dewatered feldspar concentrate is then dried and subjected to an electrostatic separation operation. A preferred electrostatic separation operation is that described by Lawver in U.S. Patent 2,805,771.

The exact reason why the treatment of the feldspar flotation concentrate containing the cationic reagent with the siliceous material prior to the electrostatic separation is beneficial is not definitely known, and it is not intended to limit the invention to any theory. However, it is believed that when the cationic reagent is added to the feldspathic material, the ions of the flotation reagent attach themselves at the sites of electrical charges on the particles and neutralize these charges. It is further indicated that the siliceous material removes the cationic reagent on the surfaces of the feldspar particles.

As hereinbefore set forth, the electrostatic separation is to a degree dependent upon the size of the particles and a preferred size range is from about 8 mesh to about 200 mesh. If the particles are not within this size range, it is preferred that the concentrate be comminuted and/ or screened. The cornminution may be performed at any suitable stage, that is, before or after treatment with the siliceous material; however, it is preferred that any comminution and/or screening be performed before the treatment with the siliceous material.

The feldspar flotation concentrate, after being treated with the siliceous material, is then further treated to develop electrical charges upon the ore particles. Before the concentrate is treated to induce the concentrate particles to accept differential electrical charges, the concentrate is preferably dried to substantially eliminate conductivity of films on the surface of the particles. When the drying is effected by heating the concentrate, a wide range of temperatures may be used, depending upon the degree of separation desired in the electrostatic separation and the nature of the feed. .The concentrate is desirably heated to dryness at a temperature of at least 150 F. and maintained at a temperature of at least 150 F. during the charging and up to the point of introduction as free falling bodies into the electrostatic field. Higher temperatures which do not deleteriously affect the mineral can be employed andin many instances are required in order to satisfactorily prepare the particle surfaces for optimum separations. In general, temperatures of between about 150 F. and 750 F. produce the desired results. Heating is generally carlied on in a preferred range of between about 400 F. and about 650 F. The effect'of this heating is evidenced by the increase in the K 0 value of the concentrate and also the improved recovery of K 0 values in the concentrate when a comparison is made between the separations accomplished after heating to the preferred range as compared to that of, for example, 200 F. Concentrates vary in composition and the optimum heating range may vary considerably, but in general will not be outside the heating range of 150 F. to 750 F. When heating at a temperature in the lower end of this range a longer period of time is usually required. The time of heating is generally'within the range of from about one minute to about two hours.

Following the heat treatment the feed material, if heated to a temperature above 450 F., is cooled to a temperature in the range of from about F. to about 450 F. and preferably to a temperature in the range of from about F. to about 350 F. Separation of heat treated material when cooled so as to be substantially cold however, can be effected.

In order to accomplish electrostatic separation either by the free fall method or by so-called conductivity separation' methods, the particles in the feed material must be induced to accept an electrical charge. When the separation is made by the free fall method, the ore particles must be dilferentially electrified before passage through the electrostatic field ie particles of gangue minerals, for example must carryian eleetrical charge of different character or ofdiiferent magnitude from h ..9 l tass aiasta Charging, in accordance with the invention, is predominantly attained through the medium of contact electrification. Contact electrification results from the movement of matter in response to such stimuli as differences in escape rate of positive or negative charges, or transfer of electrons or ions across an interface due to differences in energy levels and the like. It has been determined that real crystals never attain the static perfection of an ideal crystal lattice and that a real crystal may have distorted surfaces, displaced ions or atoms, interstitial sites and surface sites, and charge displacement due to separated anion-cation pairs of abnormal ionized atoms and trapped electrons. It is postulated that these traps are capable of acting as donors and acceptors of electrons and frequently it is these traps that are probably the controlling influences in contact electrification of minerals.

Particles of dissimilar materials, if the surfaces thereof do not exhibit differential electrification upon subjection to contact electrification operations, such as agitation, often can be caused to exhibit differential electrification by thermal, chemical, or electromagnetic methods. The differential charge may be acquired, for example, by rupture of an electrical double layer by mechanical means, as, for example, from interparticle contact and separation or by transfer of electrons from a source external to the particles, or any combination of these methods.

Basically, the desired contact electrification depends on temperature, impurity content, and mechanical history of the various surfaces involved. Therefore, it is preferable to determine the precise conditions requisite to optimum selective charging. Under certain conditions the surfaces of the mineral species are such that it is possible to electrify by mineral-metal contact electrification. For example, if such contact causes high electrification with one mineral species, a selective separation is possible. A more complete discussion of charging mechanisms may be found in Fraas et al., Industrial and Engineering Chemistry, volume 32, pages 601-602 (1940).

It has been discovered that greatly improved differential charging of the particles is accomplished in accordance with the invention by essentially particle-to-particle contact while the dry comminuted material is maintained at a temperature of at least 150 F. Ideally, the particles would not contact a metal or grounded metal surface during the charging operation. Where the charging of the particles is accomplished essentially by particleto-particle contact while at a temperature of at least 150 F.; the surface charge densities found on the mineral species in a two-component ore being equal in magnitude, and opposite in sign. Accordingly, the oppositely charged particles move in opposite directions in an electrostatic field. Thus, in the process of the invention, it becomes possible to effectively separate various species of nonconductive particles from each other,

The desired particle-to-particle charging may be effected in a number of ways, such as by tumbling the particles down an elongated chute in such quantity that contact between the particles and the chute is at a minimum. Alternatively, the comminuted mineral, while maintained at a proper temperature, may be delivered from the drying apparatus to the electrostatic separator by means of a vibrating trough. At high throughput, the great preponderance of charging is engendered by particle-to-particle contact rather than by contact of the particles with the trough. Suitable charging also may be obtained by agitation of the heated, comminuted material.

The initial beneficiation of the mineral feed is effected by passing the comminuted material as freely falling bodies through an external electrostatic field. It is desirable to the satisfactory operation of the process that the particulate minerals, when delivered to and dropped into the electrostatic field, be dry in order to achieve commercially acceptable beneficiation. Therefore, the material just prior to its entry into the electrostatic field should be at a temperature in the range from about F. to about 450 F. and preferably from about F. to about 350 F.; however, as hereinbefore set forth, higher or lower temperatures may be used. Entry of the granular material into the electrostatic field at temperatures within this range is preferred since numerous observations have shown that the best separations are achieved in this temperature range.

1 Where mineral particles are subjected to a series of electrostatic separations, the feed to subsequent stages often exhibits progressively reduced response to the electrostatic field. It is believed that this reduced response may be due to loss or leakage of charges from the granular particles or coating of the charged granular particles with fines. Such weak-responding concentrates may in one form of treatment be restored or induced to activity by passage through an impactor to create new surfaces and again recharging by frictional or other methods that give rise to differential electrification, which recharging may include a reheating in accordance with the treatment hereinabove described.

The strength of the electrostatic field which will effectively alter the path of the ore particles depends on the mass of the particle and the total surface charge on the particle. The potential gradient of the electrostatic field may vary from about 1,000 to about 5,000 volts per inch of distance between electrodes in separating material of relatively fine particle size and from about 3,000 volts to about 15,000 volts per inch for beneficiating coarser particles. In all such discussion of field strength it must be borne in mind that corona discharges which ionize air are to be avoided. In general, it is preferred to operate with a total impressed difference of potential in the range of about 30,000 volts to about 250,000 volts. This voltage should be maintained by means of a direct current potential source substantially free of ripple. A steady supply of direct current may readily be obtained by the use of such equipment as a rectified radio frequency power supply In order to give a fuller understanding of the invention, but with no intention to be limited thereto, the following specific examples are given:

EXAMPLE 1 A sample of feldspar ore'mined in the vicinity of Kona, North Carolina, was comminuted and classified to produce a substantially 20--|150 mesh fraction. In the processing of this ore to recover the feldspar, a froth flotation operation was utilized. The froth flotation operation was conducted in the presence of a cationic flotation reagent combination comprising hydrofluoric acid, an amine-type collector and an alcohol-type frother. The hydrofluoric acid was added as a 5% aqueous solution and was added in the amount of about 4 lbs. of HF per ton of ore treated. The cationic collector used was prepared by emulsifying a mixture of primary tallow oil amine acetates sold under the trade name Armac T, dehydroabietylamine acetate, and No. 2 fuel oil, in the ratio of about 1:1:2, with water to obtain a 5% solution. This collector was used in the amount of about 2.5 lbs. of reagent per ton of ore treated. The frother was methyl isobutyl carbinol and was used in the amount of about 0.6 lb. per ton of ore treated.

The mineral composition of a feldspar flotation concentrate obtained in a froth flotation process substantially as described was as follows:

A 1000 gm. portion of the concentrate was scrubbed with water at 40% solids content for 5 minutes. The

scrubbed concentrate was washed, dewatered by decantation, and heated to 580 E. for 1 /2 hours. The heated oncentrate was: cool to 0. d livqtedto aire ppe and cas a e wardly h o h Vi a ing metal trough wh ch was g un e o h e th y. an electrical conductor- Ma r in t e tou h s ed a a layer f t pthhe ma e ia was char e thereby and was then allowed to fall freely between electrodes at a rate of. appro ima y pounds Per. hou per foot of horizontal electrode width. The eleetredes consisted of two spaced rows pf 3" diameter aluminum tubes arranged with approximately 1" of space between the tubes. The rows of electrodes were approximately 10'- apart. The voltage impressed across the electrodes was 85,000, volts D.C.

Below the electrodes, 7 catch pans were properly arranged to catch the separate ore fractions. The results of the electrostatic separation are given below in Table I.

Tqble 1 The chemical analyses of the various pan products show that some separationof 'the potash spar from the soda spar was obtained. 'Pans 5 and 6 were combined for analysis, as is designated by the brackets in the table.

A second 1000 gm. portion of the feldspar flotation concentrate was scrubbed for 5 minutes at 40% solids with Na SiO (N a O:'SiO =1:l) in the amount of 20 pounds per ton of solid concentrate. The pH of the slurry during scrubbing was about 11.5. The scrubbed material was washed, dewatered by decantation, and heated at 580 F. for 1 /2 hours. The heated concentrate was cooled to 300 and subjectedto an electrostatic separation substantially the same as utilized to beneficiate the first 1000 gm. sample. The results of the electrostatic separation are given below in Table II.

By comparing the results shown in Table H with the results shown in Table I, it may be'seen that the treatment with sodium silicate was beneficial. A higher yield of a higher grade K 0 concentrate was obtained using the process of this invention. V r

A third 1000 gm. portion of the feldspar flotation concentrate was scrubbed for 5 minutes at 40% solids with Na SiO (Na O:SiO =1:1) in the amount of 10 pounds per ton of solid concentrate. The pH of the slurry during scrubbing was about 10. The scrubbed material was washed, dewatered by decantation, and heated at 580'F. for 30 minutes. The heated concentrate was cooled to 300 F. and subjected to an electrostatic separation substantially thesame as utilized to beneficiate the t y qasl .m rt asd .1 99 sample 'I e rssults of the electrostatic separation are presented below in Table III.

Table III wt. wt. Wt. Pan Percent Percent Percent 6.9 i 2.6 5.3 13.7 2.2 7.5 18.5 3.0 7.7 21.8 as 6.2 14.0 2.1 5.0 11.5 9.2 4.0 13.0 9.6 3.3

Composite 100.0 5.9- e 5.8

A comparison of the results presented in Table III with the results presented in Table II shows that the treatment with only one-half the amount "of sodium silicate at a lower pHwas beneficial;

ou h 00' Pa isan cf th f lds a qt concentrate was scrubbed for 5 minutes "at 40% "solids with Na SiO (Na O:SiO 1:1) in the amount of '20 pounds per ton of solid concentrate.""The of the slurry during scrubbing was adjusted to about 5.5 with H 30 The scrubbed material was washed, dewatered by decantation, and heated at5 80 F. for 1 /2 hours. The heated concentrate'was cooled to 300? F; and subjected to an electrostaticseparation substantially the same as utilized to beneficiate the previously mentioned 1000 gm. samples. The results of the electrostatic"separation are tabulated in Table IV.

Table IV 'wt. Wt. Wt. Pan Percent Percent Percent K10 'Na' Q 7. s 2.2 5.4 10.5 1.5 8.1 20.3 as as 21.6 6.4' 5.5 12.9 8.9 4.1 10.1 9.0 3.7 10.8 10.3 2.9 Composite 109.0 as 5.5

The resultspresented in Table IV are seen to be superior to the results presented in Tables I, II, and III, thus illustrating the advantage of serubbing with sodium silicate at a lower pH. fl

Another noteworthy feature of the novel process utilizing sodium silicate described herein is the tendency for both mica and quartz to concentrate in pan 1, enabling the production of cleaner potash spar and soda'spar concentrates.

' EXAMPLE 2 Another sample of feldspar flotation from Kona, North Carolina, prepared in a manner similar to the sample cited in Example 1, was found to' have thefollowing mineral composition:

Percent Potash spar 47 Soda spar i 48 Quartz 4 Mica e 1 :1 a e t e ttsq e s awat r l iti aware: d

9 scribed in Example 1. The voltage impressed across the electrodes was 80,000 volts DC.

The electrostatic separation results obtained are tabulated in the following Table V:

A moderate separation of the potash spar from the soda spar was observed as illustrated by the results presented in Table V.

A second 1500 gm. portion of the feldspar flotation concentrate was subjected to the same H SO -Na SiO treatment just described. However, the washed, dewatered concentrate was heated for 1 /2 hours at 560 F., cooled to 300 F., and subjected to the same electro static separation procedure just described.

The results of the electrostatic separation are shown in Table VI.

The results presented in Table VI are seen to be superior to the results presented in Table V.

A third 1500 gm. portion of the feldspar flotation concentrate was subjected to the same H SO -Na SiO treatment just described. In this instance, the washed, dewatered concentrate was heated for 1 /2 hours at 640 F., cooled to 300 F., and subjected to the same electrostatic separation procedure just described.

Table VII presents the electrostatic separation results obtained.

Table VII Wt. Wt. Wt. Pan Percent Percent Percent K20 NagO Composite 100. O 6. 4 6. 1

The results presented in Table VII are seen to be slightly inferior to the results presented in Table VI.

EXAMPLE 3 A 1,000 gram portion of the feldspar flotation concentrate prepared in Example 1 was scrubbed for 4 minutes at 40% solids with precipitated silica used in the amount of pounds per ton of solid concentrate. The pH of the slurry during scrubbing was adjusted to about 8.2 by

the addition of sodium hydroxide. The scrubbed material was washed, dewatered by decantation, dried at 300 F., and heated at 585 F. for 2 hours. The heated concentrate was cooled to 325 F., delivered to a feed hopper, and subjected to electrostatic separation utilizing the apparatus described in Example 1. The voltage across the electrodes was 85,000 volts DC.

The electrostatic separation results obtained are tabulated in the following Table VIII. Pans 6 and 7 were combined for analysis, as is designated by the brackets in the table.

Table VIII Wt. Wt. Wt. Pan Percent Percent Percent K20 N e 0 7 e. a 11. o 1. 5

It should be noted that good results were obtained using precipitated silica to treat the flotation concentrate.

The description of the invention utilized specific reference to certain process details, however, it is to be understood that such details are illustrative only and not by way of limitation. Other modifications and equivalents of the invention will be apparent to those skilled in the art from the foregoing description.

Having now fully described and illustrated the invention, what is desired to be secured and claimed by Letters Patent is set forth in the appended claims.

I claim:

1. A process for beneficiating a feldspar flotation concentrate which comprises treating a feldspar flotation concentrate obtained in a cationic flotation operation with a siliceous material selected from the group consisting of silicon, silica, alkali metal silicates and ortho silicate esters, heating the treated concentrate, inducing the heated concentrate to accept an electrical charge, and subjecting the charged concentrate to an electrostatic separation.

2. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation which comprises treating said feldspar flotation concentrate with precipitated silica, heating the treated concentrate, inducing the heated concentrate to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

3. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation which comprises treating said feldspar flotation concentrate with an alkali metal silicate, heating the treated concentrate, inducing the heated concentrate to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

4. The process of claim 3 wherein said alkali metal silicate comprises sodium silicate, having an SiO to Na O mole ratio within the range of from about 1:1 to about 3.75:1.

5. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation using a cationic flotation reagent which comprises slurrying said feldspar flotation concentrate, while still containing cationic flotation reagent, with a siliceous material selected from the group consisting of silicon, silica, alkali metal silicates and ortho silicate esters, heating the treated concentrate, inducing the heated concentrate to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

6. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation using a cationic flotation reagent which comprises slurrying said feldspar flotation concentrate, while still containing cationic flotation reagent, in aqueous solution, with precipitated silica, heating the treated concentrate, inducing the heated concentrate to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

7. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation usinga cationic flotation reagent which comprises slurrying said feldspar, while still containing cationic flotation reagent, in aqueous solution with an alkali metal silicate, heating the treated concentrate, in ducing the heated concentrate to accept diflerential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

8. The process of claim 7 wherein said alkali metal silicate comprises sodium silicate having an SiO to Na O mole ratio within the range of from about 1:1 to about 3.75:1.

'9. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation using a cationic flotation reagent which comprises slurrying said feldspar flotation concentrate, while still containing cationic flotation reagent, in aqueous solution with a siliceous material selected from the group consisting of silicon, silica, alkali metal silicates and ortho silicate enters in amount of from about 0.05 to about 50 lbs. of siliceous material per ton of concentrate, heating the treated concentrate, inducing the heated concentrate to accept diflerential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

10. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation using a cationic flotation reagent which comprises slurrying said feldspar flotation concentrate, while still containing cationic flotation reagent, in aqueous solution w th a siliceous material selected from the group consisting of silicon, silica, alkali metal silicates and ortho s.licate esters in amount of from about 0.50 to about 40 lbs. of siliceous material per ton of concentrate, heating the treated concentrate, inducing the heated concentrate to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

11. A process for beneficiating a feldspar flotation cone centrate which comprises slurrying a feldspar flotation concentrate obtained in a cationic flotation operation in aqueous solution with a siliceous material selected from the group consisting of silicon, silica, alkali metal silicates and ortho silicate esters at a pH in the range from about 2.0 to about 12.0, heating the treated concentrate, inducing the heated concentrate to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

12. A process for beneficiating a feldspar flotationconcentrate which comprises slurrying a feldspar flotation concentrate obtained in a cationic flotation operation in aqueous solution with an alkali metal silicate at a pH in the range from about 2.0 to about 12.0, heating the treated concentrate, inducing the heated concentrate to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

13. A process for beneficiating a feldspar flotation concentrate which comprises treating a feldspar flotation concentrate obtained in a cationic flotation operation with a siliceous material selected from the group consisting of silicon, silica, alkali metal silicates and ortho silicate esters, heating the treated concentrate to a temperature within the range from about 15.0". F. to about 750 F., inducing the heated concentrate to accept an electrical charge, andsubjecting the charged concentrate to an electrostatic separation.

14. A process for beneficiating a feldspar flotation concentrate obtained as a float product'in a cationic flotation operation using a cationic flotation reagent which comprises slurrying said feldspar flotation concentrate while still containing cationic reagent, in aqueous solution with a siliceous material selected from the group consisting of silicon, silica, alkali metal silicates and ortho silicate esters, heating the treated concentrate to a temperature within the range of from about F. to about 750 F., inducing the heated concentrate, while at a temperature within the range of from about'l50' F. to about 350 F. to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

15. The process of claim 14 wherein said siliceous material comprises an alkali metal silicate.

16. The process of claim 15 wherein said alkali metal silicate comprises sodium silicate having an SiO to Na O mole ratio within the range of from about 1:1 to about 3.75:1. i i

17. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation using a cationic flotation reagent which comprises slurrying said feldspar flotation concentrate, while still containing cationic flotation reagent, in aqueous solution with a siliceous material selected from the group consisting of silicon, silica, alkali metal silicates and ortho silicate esters in an amount of from about 0.05 to about 50 lbs. of siliceous material per ton of concentrate, at a pH within the range of from about 2.0 to about 12.0, heating the treated concentrate, inducing the heated concentrate to accept differential electrical charges, and subjecting the charged concentrate to an electrostatic separation.

18. A process for beneficiating a feldspar flotation concentrate obtained as a float product in a cationic flotation operation using an amine type flotation reagent which comprises scrubbing said feldspar flotation concentrate with sodium silicate in an amount of from about 0.50 to about 40 pounds of sodium silicate per pound of feldspar flotation concentrate treated, said sodium silicate having an SiO to Na O mole ratio within the range of from about 1:1 to about 3.75:1, at a pH within the range of from about 2.0 to about 12.0, washing said scrubbed concentrate with water, heating the washed concentrate to a temperature within the range of from about 150 F. to about 750 F., inducing the heated concentrate While at a temperature within the range of from about 150 F. to about 450 F. to accept diflerential electrical charges, and thereafter subjecting the diflerentially charged concentrate as free falling bodies and while at a temperature of at least 150 F. to an electrostatic field to beneficiate the concentrate.

19. The process of claim 3 wherein said siliceous material comprises silica.

20. The process of claim 19 wherein said silica comprises silica gel.

21. The process of claim 19 wherein said silica. comprises colloidal silica.

22. The process of claim 3 wherein said siliceous material comprises an alkali metal silicate;

23. The process of claim 22 wherein said alkali metal silicate comprises 'a sodium silicate solution.

References Cited in the file of this patent UNITED STATES PATENTS Johnson, Apr. 23, 1 9740 Lawver Sept. 10, 195.7 

